In recent years, by the introduction of FIT (Feed-in Tariffs) or others, the market of a large-scale photovoltaic system which is so-called mega solar system or others having an output equal to or larger than 1 megawatt has been expanded. In the mega solar system, several thousands to several tens of thousands of sheets of a PV module whose class is 100 W to 200 W is arranged at one location in a PV power site.
As a method of detecting a failure in a PV module, there are methods such as inspecting a deterioration of a cell by visual inspection, a method of detecting the presence or absence of abnormal heat generation of a cell by a thermometer, and a method of inspecting electrical property such as current-voltage property by a tester. These inspections are normally performed to each of a PV module or PV string (hereinafter, simply referred to as a “PV module” in some cases).
As a technique related to this, for example, Japanese Patent Application Laid-Open Publication No. 2010-123880 describes a technique of determining whether a failure has occurred in the PV module or not by providing measuring means and communicating means for each PV module or string, transmitting a measured property value and an identification signal of the PV module to a control device, and comparing the transmitted result with a previously-set threshold.
Also, Japanese Patent Application Laid-Open Publication No. 2011-146472 describes a technique of determining a high-temperature portion on a surface of a PV array as failure by an imaging machine which performs infrared-ray imaging of the surface of the PV array, by a moving mechanism which moves the imaging machine, by an observation monitor which displays an image obtained by the infrared-ray imaging by the imaging machine moved by the moving mechanism, and by a control device which controls the infrared-ray imaging of the imaging machine and the movement of the moving mechanism.